1. Field of the Invention
The present invention relates to a bonding die for use in bonding a trim cover assembly to a foam cushion member so as to form an automotive seat, and is in particular directed to a pressure-bonding die of this kind on which the trim cover assembly is placed for a pressure bonding with the foam cushion member.
2. Description of Prior Art
As one of means for forming a seat for automobile, a bonding die is made available, by which a trim cover assembly is pressed and bonded to the outer surfaces of a foam cushion member. Reference is made to FIG. 1 which shows a typical conventional pressure-bonding die apparatus comprising a stationary lower die member (L') and a movable upper die member (U') which may be moved vertically by operation of a cylinder (D') towards and away from the lower die member (L'). A foam cushion member (P) and a trim cover assembly (C) are secured to the upper and lower die members (U')(L'), respectively. As shown by way of example in FIG. 2, the foam cushion member (P) and trim cover assembly (C) are pressed and bonded together by the die apparatus to produce a seat cushion (SC) for automotive seat, which has uneven outer shape. Thus, the cushion member (P) is formed to have a flat central seating portion (22) and a pair of lateral raised bolster portions (23)(23), whereas the trim cover assembly (C) is formed by sewing together a central cover section (10) and a pair of lateral cover sections (11, 12)(11, 12) such as to cover the central and paired bolster portions (22)(23) of cushion member (P), respectively. Naturally, in the trim cover assembly (C), a pair of spaced-apart upheld connected portions (F)(F) are created, projecting towards the reverse side of trim cover assembly (C), with a pair of valley-like groove portions (G) (G) being created at the respective portions corresponding to those two connected portions (F)(F) at the front side of trim cover assemlby (C), as can be seen in FIG. 2. In operation, the trim cover assembly (C) is reversed and placed on the lower die member (L') and then, the two connected portions (F)(F) are respectively inserted and bonded to two recessed grooves (21)(21) formed in the foam cushion member (P). The lower die member (L'), in order to permit fit and neat placing of such trim cover assembly (C) thereon, is so formed to have, defined in its outer die surface, a flat die surface (L'1), a pair of lateral curved die surfaces (L'2)(L'2) and a pair of upwardly projected retaining portions (L'3)(L'3). Hence, when placing the trim cover assemlby (C) upon the lower die member (L'), the central and lateral cover portions (10)(11) are respectively placed on the flat and curved die portions (L1')(L'2), while insuring that the two retaining portions (L'3)(L'3) are fitted in the respective two valley-like groove portions (G)(G), as in FIG. 1. Then, after applying an adhesive to either of the trim cover assembly (C) and cushion member (P), the upper die member (U') is lowered towards the lower die member (L') so that the trim cover assemlby (C) is bonded to the cushion member (P) along their mutual mating surfaces to provide a bonded unit of them. The bonded unit is removed from the base die member to finally produce a seat or a part of seat such as the seat cushion (SC) or a seat back.
However, the foregoing conventional pressure-bonding die apparatus has been found defective in that, after the bonding process, a bonded unit of trim cover assembly (C) and cushion member (P) can hardly be removed from the uneven surfaces of lower die member (L') because the outward expanding mass of foam cushion member (P) forcibly causes the bonded unit on the whole to resiliently stick to or embrace both curved die surfaces (L'2)(L'2) of lower die member (L'). Moreover, the fact that the retaining portions (L'3) of lower die member (L') are fitted in the trim cover assembly groove portions (G) renders it harder to remove the bonded unit from the lower die member (L') and also gives rise to an extreme drag or friction between those groove and retaining portions (G)(L'3) when causing the bonded unit to be removed from the lower die member (L'). Thus, removel of the bonded unit from the lower die frequently tears or damages the trim cover assembly (C).